Stanley Fischer, the vice chairman of the Federal Reserve, has announced that he will retire next month, creating a third vacancy for President Donald Trump to fill at the bank.

The 73-year-old will step down on October 13.

This is nearly a year before his term as vice chair was due to expire and two and a half years before the end of his term on the Fed's board of governors, the Fed said in a statement.

In a letter of resignation, Fischer said he was stepping down for unspecified "personal reasons" and cited the Fed's work to stabilise the US financial system following the 2008 global financial crisis.

Trump in July chose the investor and former Treasury Department official Randal Quarles to join the Fed as vice chair for supervision in a further sign the White House may promote continuing deregulation of the financial sector. 

Trump has said he is also weighing whether to name his current senior economic advisor Gary Cohn as Fed chair, replacing Janet Yellen, whom he has also said he may keep in place.

In a recent speech, Yellen delivered a forceful defence of Wall Street reforms put in place after the crisis, widely seen as a direct contradiction of Trump's position which could cause her to lose favor in the White House.

Former Board of Governors member Daniel Tarullo stepped down in April. 

Fischer, a former governor of the Bank of Israel and vice chairman of Citigroup, leaves the Fed as it confronts the deepening dilemma of US monetary policy.  

Policymakers have twice raised rates in 2017 but a third rate hike this year is seen as increasingly unlikely because inflation has failed to rise despite persistent job growth.